During the past decade there has been a proliferation of methods to grow diamond crystals and films. Most of these methods are based on decomposition of a gaseous hydrocarbon source, and a common substrate is single crystal silicon. Some metals, such as molybdenum and nickel, also have been used as substrates. These substrates are frequently scratched with fine diamond particles and these particles become seeds for growth. Reviews of these works can be found in the literature, and an example is W. A. Yarbrough and R. Messier, Science 247, 688 (1990). The role of the diamond seed is given by S. Iijima, Y. Aikawa, and K. Buba, Applied Physics Letters 57, 2646 (1990).
Recently, a substantially new method has been presented by J. F. Prins, and H. L. Gaigher, Second International New Diamond Science and Technology Conference, Washington, D.C., Sep. 23-27, 1990. In this method, carbon ions are implanted into a hot substrate, and an outdiffusion of the carbon onto the substrate surface forms a heteroepitaxial growth of diamond. The authors call this method "implanted-atom-outdiffusion-epitaxy (`IAOE`)". The IAOE method has three disadvantages:
1. The penetration depth of ion implantation is limited to tens of nanometers and all the diamond growth is limited to this superficial region.
2. The use of ion implantation to place a large quantity of carbon ions through either a high ion beam current or a prolonged implantation time is neither economical nor practical. One drawback is a limitation of the thickness of the diamond layer to a submicron dimension. Moreover, in order to produce a thicker film, the process must be altered by using, for example, CVD to grow epitaxially on the ion implantation produced film.
3. High energy carbon ions produce radiation damage on the substrate and destroy the crystal perfection of the substrate. The resulting defects can be transmitted to the epitaxial layer with a concomitant agglomeration of defects.
It is accordingly a general object of the invention to eliminate the disadvantages of the IAOE method.